A 2018 Summer of Extremes

Meteorological summer has been one of extremes in the U.S. Overall, the East has been wet while the West has baked in the heat. These types of extremes, which are set up by a consistent jet stream pattern, are amplified by a warming climate.

Many locations in the Middle Atlantic, Ohio Valley, and Upper Midwest had one of their 10 wettest summers on record, with Maryland and Pennsylvania at the heart of the summer deluge. Baltimore was among the cities in their top 10, getting more than 24 inches of rain. Massive flooding hit central and eastern Pennsylvania in July. More than 15 inches of rain fell in the town of Lebanon in July, and 12-15 inches were common monthly totals around the state capital of Harrisburg. The supercharged water cycle that comes with a warming climate is reflected in the increase in heavy precipitation. The heaviest rainfall events are getting heavier, with a 55 percent increase in the amount of precipitation falling in the heaviest events in the Northeast.

Even in the unrelenting summer heat in the Southwest, occasional summer monsoon thunderstorms can provide some relief from the heat. Enough of them came together to give Prescott, Arizona one of its 10 wettest summers on record.

Nearly all states across the U.S. have sites with one of their 10 hottest summers on record, but the core of the heat has been in the Southwest, and that continues to play a role in the devastating wildfire season in California. The Mendocino Complex fire north of San Francisco is the largest on record in the Golden State. At 422,000 acres, that size translates to 660 square miles, or a little more than half of the state of Rhode Island. This summer has also brought the Carr Fire, the state’s seventh largest on record near the city of Redding. In a warming climate, there is more drying of vegetation, providing more fuel for fires in the West. In fact, five of the seven largest fires on record in California have come since 2012. The smoke from the western wildfires has worsened air quality in much of the country, which is more than just an eyesore, it affects human health.

The U.S. has come a long way in cleaning up its air. The Clean Air Act of 1970 made air pollution catastrophes like the 1948 smog that killed nearly 40 people near Pittsburgh a distant memory. But while the air is much cleaner overall, smoke from wildfires is threatening the progress that’s been made, as particulate pollution from wildfires has

In a warming world, a supercharged water cycle ramps up evaporation and precipitation. Warmer air creates higher evaporation rates from the soil, which worsens drought, stresses water supplies, and hampers agriculture. Evaporation of surface waters, such as lakes and oceans, also increases. A warmer atmosphere can hold more water before becoming sa

With flooding in parts of the Mississippi Valley and a strong Pacific storm coming into the Northwest, we examined the trend in the number of days each year with heavy precipitation at 244 individual sites in the U.S. This expands our nationwide-averaged heavy precipitation analysis from earlier this year, complementing the 2017 Climate Science